Knob and shaft construction



24, 1939. N. c. SCHELLYENGER ,2 7

KNOB AND SHAFT CONSTRUCTION Filed Nov. 22, 1937 Patented Oct. 24, 1939 PATENT OFFICE KNOB CONSTBUCTIOH Ncwton'C. Schcllenger, Elkhart, Ind., assignor to Chicago Telephone- Supplybompany, Elkhart, Ind., a corporation of Indiana Application November 22, 1937, Serial No. 175,798

30mins.

This invention relates to a new and improved knob and shaft construction and more particularly to such'a construction especially adapted for use with radio set or test instrument controls or the'like The methods in commercial use for securing knobs to shafts with such apparatus have consisted of twogeneral types. The most usual type comprises a set-screw threaded in a knob and for maximum efliciency this requires a solid shaft with a flattened face toreceive the set-screw. The other type comprises several modifications all of which'include springs carried either by the shaft or by the knob. Both types require additional parts other than the knob and shaft,

' such as set-screws or springs.

It is an object of the present invention to provide a new and improved knob and shaft con struction.

It is a further object to provide a construction Figure 1 is an elevation of a control with my improved knob and shaft applied thereto;

Figure 2 is a sectional view showing the shaft end and knob in unassembled relation;

Figure 31s a section taken on line 3-3 of Figure 1; and m 'Figure 4 is an end view of the shaft.

Referring first to Figure l, the control housing il may enclose a device such as a switch or a variable resistance which is actuated or varied by the rotation of the shaft II which extends- 5 through the threaded bushing I3 by'means of which the device may be secured to a chassis or.

panel or the like. The knob I4 is secured upon the end of the shaft. n

As clearly shown in the'drawing, the shaft is made of sheet metal which is rolled to form a tubular member with the edges of the sheet ad-- jacent each other. These edges are sloped apart as shown'at 15 adjacent the free end of the shaft to form a tapering,.wedge-shaped recess. The a knob i4 is provided with the substantially cylindrical inner opening I6, adaptedto' fitover the end-ofthe shaft L2. The inner face of this opening it carries the securing lug H which is similar in form to the tapering recess I5 in the end of the shaft.

The knob is assembled upon the shaft by moving it axially onto the shaft with the lug, H in registration with the recess If: in the shaft wall.

.It may be firmly seated by means of a light blow silient so that the knob is held firmly in place.

The wedging action of the lug ll in the recess it serves to expand the shaft circumferentially so 35 that it positively engages the wall of the opening IS. The knob may be removed by loosening it by a blow on the side or directed slightly outward from the control to which the shaft is connected. The-securing action of the wedge lug I? has no tendency to compress or distort the shaft as is the case when set-screws are used to secure knobs to hollow shafts. When a lamb of this type is secured to a hollow shaft having other control means extending through the opening in the shaft, there is no tendency to bind the inner control. The action of the knob securing wedge expands the shaft rather than contracts it. The edges of the split in the shaft may be slightly roughened as the material is cut to form the splitl so This roughened edge will bite into the wedge and assist in preventing undesired separation of the parts after assembly.

Hollow shafts of this character require considerably less metal than solid shafts of the same 35 size, and since the shafts of controls are often formed of copper bearing alloys, the saving in metal cost may be considerable in quantity production. 4 V i In addition to this a substantial saving is efw fected in the time and expense of making the complete shaft from the raw material as my construction requires only a simple and quick punch press operation whereas the conventional solid shaftrequires relatively difflcult and slow opera- 4,5 tions in both automatic screw machines and milling' machines.

while I have shown a preferred form of construction, this'is to-be understood to be illustrative only. It will be understood that the knob may have any desired form or construction. The lug II may be formed integrally with the knob which consists of Bakelite or other similar material. The lug l'l may, however, if desired, be

. madebf metal and inserted in the knob during the molding operation or secured therein in any desired manner.

spirit and scope of the appended claims.

I claim: r g

1. In combination: a cylindrical tube slit longitudinally from end to end and formed of resiliently deformable metal with the edges of the slit in juxtaposition; a knob having a substantially cylindrical cavity to loosely receive an end portion of the tube, and means in said cavity for expanding the tube into firm engagement with the side wall of the cavity as it is inserted to thereby removably secure the knob to the tube.

2. In combination: a cylindrical tube slit longitudinally from end to end and formed of resiliently deformable metal with-the edges of the slit in juxtaposition; a knob having a substantially cylindrical cavity to loosely receive an end portion of the tube; and a wedge shaped lug on the side wall of the cavity adapted to be forced into the slit during the application of the knob to I contemplate such otherchanges and modifications as come within the the tube to spread apart the edges of the slit and expand the tube into firm frictional engagement with the side wall of the cavity as it is 'inan outwardly flaring mouth for the slit; a knob having a substantially cylindrical cavity to loosei ly receive said end portion of the tube; and a lug on the side wall of the cavity positioned to enter the flaring mouth of the slit during application of the knob to the tube to spread apart the edges oft-he slit and thereby expand the tube into firm frictional engagement with the side wall of the cavity as it is inserted to removably and nonrotatably secure the knob to the tube.

NEWTON C. SCHELLENGER. 

